Pears tend to be more susceptible than apples.Ĭommercial growers can use bactericidal sprays, such as copper sulfate or streptomycin, during the bloom period. Although they are not completely immune to fire blight, resistant varieties are less impacted by the disease than are other varieties. Resistant varieties should be planted whenever possible. Infected branches should be pruned at least 12 inches below the area that looks diseased, to remove all of the bacteria. It is best to prune when the plant and bacterium are dormant, during the winter. Sanitation is most important, and infected branches should be pruned out of the tree. Several management tactics can help reduce the impact of fire blight. Want to submit a sample? Follow the foliar instructions on the tree and small fruits or trees and shrubs (woody plants) pages.įire blight on apple fruit, note the bacterial ooze (milky droplets- signs) If your sample is from outside of Iowa, please do not submit it to the Plant & Insect Diagnostic Clinic without contacting us. Contact information for each state's diagnostic laboratory for U.S. Please see our website for current forms, fees, and instructions on collecting and packing samples. The Iowa State University Plant & Insect Diagnostic Clinic can help you investigate and confirm if your plant has this disease. Type of Sample Needed for Diagnosis and Confirmation Healthy plants may become infected through blossoms or wounds. In the springtime, sticky bacterial ooze formed at the edges of the cankers is carried to healthy plants by insects, wind, and splashing rain. The bacterium survives the winter in cankers on infected branches. Disease cycle of fire blightįire blight is caused by a bacterium Erwinia amylovora. During wet weather, bacteria may also ooze and later dry to a white residue in shoot, flower or fruit. Signs of fire blightĬankers and the blighted shoots may produce sticky ooze (signs) in wet weather. Cankers (areas of sunken or discolored bark) may develop on limbs, and the blighted shoots may produce sticky ooze (signs) in wet weather. The most characteristic symptom is the curling of affected shoots into curved "shepherd's crooks". Leaves on affected branches wilt and turn black, appearing as if scorched by fire. Infected branches should be pruned to reduce impact.įire blight is a common springtime disease of apple, pear, and related species, including crabapple, hawthorn.Bacterial ooze is transmitted by insects, wind, and splashing rain to infect healthy plants.Affected leaves will blight and turn black and affected shoots will curl.Avoid the use of high nitrogen fertilization, which promotes increased shoot elongation.During growing season prune at least 12 inches below the diseased area and disinfect pruners between cuts.During dormancy (dry weather) prune infected branches.Cambistat, a tree growth regulator, can also be used to minimize shoot growth, which will minimize the shoot blight stage of a fire blight infection. A foliar spray treatment in the spring temporarily suppresses rapid shoot elongation during the peak infection period by the fire blight pathogen potentially reducing the susceptibility of the host to shoot tip infections. Trimtect does not have direct antibiotic activity against the fire blight pathogen ( Erwinia amylovora), but can reduce the host susceptibility. If not managed, fire blight can destroy the blossoms, fruit, and stems of the plant, and even kill the plant. Treat trees that expressed visible symptoms in previous growing seasons or high value trees growing adjacent to symptomatic trees.
A combination of cultural practices to reduce tree susceptibility and disease spread, and chemical control to protect against infection can reduce the disease. There is no single management practice that completely controls fire blight.
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